Over Reving Question

[ViperJ]

Okay first let me say this is my first manual car so I dont know much about the manual tranny's. My question is what actually happens when you continously over rev your engine. I know it does damage but what gets damaged? Second I have my camaro that I guess redlines (the red line starts) at 6,000 is that were I would want to shift when racing? Thanks for the help

[duplox]

Originally Posted by ViperJ

Okay first let me say this is my first manual car so I dont know much about the manual tranny's. My question is what actually happens when you continously over rev your engine. I know it does damage but what gets damaged? Second I have my camaro that I guess redlines (the red line starts) at 6,000 is that were I would want to shift when racing? Thanks for the help

Lots of things can happen. From as mild as excessive cylinder wear or overheating to cracking a cylinder, snapping a rod, etc.
Second question.. not neccesarily, and probably not. It depends entirely on the engine. Redline is just where the factory decides its no longer safe to rev it over this point, your peak power is probably around 500rpm below factory redline. I know several drag racers who shift differently in each gear - generally, the higher the gear, the lower RPM they shift out. The difference is only a few hundred RPM, but it shaves a few thousandths off their times. The only way to really tell is trial and error - go to the track and keep running until you find what works best. I'd guess shifting at 5500-5750 would give you best results with a 6000rpm redline.

[benchtest]

In my experience, pushing a stock engine over red-line results in valve float. That can lead to results that vary from no damage to catastrophic damage. As Duplox stated, there is no more power up there...so it's foolish to do it.

[duplox]

Originally Posted by benchtest

In my experience, pushing a stock engine over red-line results in valve float.

Dur, how'd I forget that one... thanks. Basically, it could lead to lots of things. There is no point to doing it, so don't risk it.

[SaabJohan]

Overreving usually result in valvetrain damage or failure. Conrods breaking is another common result of overreving.

However, on most newer engines it's impossible to overrev the engine unless you gets the wrong gear in.

As a general rule of thumb a driveable racing engines should be able to rev 500 to 1000 rpm over peak power and for maximum performance you must usually go there. Most road engines are capable of this aswell.

There's a simple way to calculate where to change gear on just your car. Use a software like Microsoft Excel, write down the torque produced by the engine against rpm in a list. Write down the gear ratios in another list. Then you multiply the torque produced by the engine with the gear ratios and make a graph of this against wheel velocity which you calculate from gear ratio and engine speed. The acceleration will be the highest where the torque on the wheel axles are highest. When the torque at the lower gear/higher engine speed is equal to the torque produced by the higher gear/lower engine speed it's time to change gear.